Thank you for your post.
I am unable to replicate the issue This is what I have done.
1. Using FileMaker Pro 13.0v1 on Mac OS X 10.8.5, I created two tables "Names" and "Invoices". I created a relationship between "Names" and "Invoices" via the field ID.
2. On the Layout that contains Names, I created a Portal into Invoices showing the fields Date, Invoice Number, and Total Amount.
3. In Layout Mode, I pulled down the View menu and made sure Inspector was being viewed.
4. I clicked once on the portal to select it, and in the Inspector, I clicked the Appearance tab.
5. In the top section, I left it at my default of Theme: Enlightened, and Style: Default*
6. Below that, the pop-ups displayed Portal and Normal.
7. In the Graphic section beneath that, there was no fill, but I set the portal to display a border around the entire portal, and I set the line to 1 point with color black.
8. At the top, I changed the pop-up from Portal to "Portal Row".
9. In the Graphic section below, I set the Fill Color to solid white, Set the line to Solid 1 point and black color, and selected the bottom edge.
This now shows a double-edge for the bottom, so I changed the pop-up back to Portal, and changed the bottom border to not appear.
Let me know what I'm doing differently than you so I can try to replicate the issue.
Your answer solved the problem. I was unaware of the "portal row" pop-up selector. As soon as you pointed it out, I wondered how I could have missed it. FM12 isn't as fine-grained in its control, so it handled both the row and the outside borders.
I'd looked through the documentation before putting up my original post, but I clearly missed this. A second more thorough search revealed the answer.
For those who are interested, it's located here:
Home > Designing and Creating databases > Editing objects, layout parts, and the layout background > Formatting objects, layout parts, and the layout background > Formatting portals
Thanks very much for your help.